Ben Creisler
Some recent paleo-topic papers that may be of interest:
Matthew P. J. Oreska and Matthew T. Carrano (2018)Â
Paleocommunity mixing increases with marine transgression in Dinosaur Park Formation (Upper Cretaceous) vertebrate microfossil assemblages.
Paleobiology (advance online publication)
Vertebrate microfossil assemblages in a stratigraphic sequence often yield similar assortments of taxa but at different relative abundances, potentially indicative of marginal paleocommunity changes driven by paleoenvironmental change over time. For example, stratigraphically younger assemblages in the Dinosaur Park Formation (DPF) yield proportionally more aquatic taxa, consistent with marine transgression. However, individual deposits may have received specimens from multiple source paleocommunities over time, limiting our ability to confidently identify ecologically significant, paleocommunity differences through direct assemblage comparisons. We adapted a three-source, two-tracer Bayesian mixing model to quantify proportional contributions from different source habitats to DPF microfossil assemblages. Prior information about the compositions of separate, relatively unmixed terrestrial, freshwater, and marine assemblages from the Belly River Group allowed us to define expected taxon percent abundances for the end-member habitats likely contributing specimens to the mixed deposits. We compared the mixed assemblage and end-member distributions using 21 different combinations of vertebrate taxa. Chondrichthyan, dinosaur, and amphibian occurrence patterns ultimately allowed us to parse the contributions from the potential sources to 14 of the 15 mixed assemblages. The results confirmed a significant decline in terrestrial contributions at younger DPF sites, driven primarily by increased freshwater specimen inputsânot incursions from the adjacent marine paleocommunity. A rising base level likely increased lateral channel migration and the prevalence of freshwater habitats on the landscape, factors that contributed to increased paleocommunity mixing at younger channel deposit sites. Bayesian methods can account for source-mixing bias, which may be common in assemblages associated with major paleoenvironmental changes.
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Vivesh V. Kapur &Â Ashu Khosla (2018)
Faunal elements from the Deccan volcanoâsedimentary sequences of India: A reappraisal of biostratigraphic, palaeoecologic, and palaeobiogeographic aspects.
Geological Journal (advance online publication)
The sedimentary sequences associated with the Deccan Flood Basalts, i.e., infratrappean and intertrappean deposits, are known to yield a diverse assemblage of fauna that includes foraminiferans, ostracods, molluscs, fishes, frogs, turtles, lizards, snakes, crocodiles, dinosaurs, and mammals. The existing literature debates the exact nature of origin, age, and duration of the Deccan volcanic activity; however, there is a general accord within the geosciences community that the Deccan Flood Basalts bestrode the CretaceousâPalaeogene Boundary. Within the past few decades, the record of the biotic component (particularly faunal elements) reported from the Deccanâvolcano sedimentary sequences have grown both numerically and taxonomically. Constraining the age of the Deccanâvolcano sedimentary sequences has a direct bearing on the studies that discuss the origin, evolution of the biota in a palaeobiogeographic framework, and also in the context of changes in the palaeoenvironment and palaeoecology. Thus, it becomes important to reinforce the age, environment of the Deccanâvolcano sedimentary sequences, and the origin/affinity of the faunal elements recovered from within these sedimentary deposits. We here reappraise the biotic (with an emphasis on the fauna) evidence in a biostratigraphic, palaeoecologic, and palaeobiogeographic aspect.
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Free pdf:
Jinnan TONG, Daoliang CHU, Lei LIANG, Wenchao SHU, Haijun SONG, Ting SONG, Huyue SONG & Yuyang WU (2018)
Triassic integrative stratigraphy and timescale of China.ÂÂ
SCIENCE CHINA Earth Sciences (advance online publication)
The Triassic rocks are widespread in China, and both marine and terrestrial strata are well developed. The Triassic stratigraphic architecture of China is very complex in both spatial variation of the so-called "South Marine and North Continental", i.e. the southern areas of China occupied mostly by marine facies while the northern China by terrestrial facies during the Triassic Period, and temporal transition of the âLower Marine and Upper Continentalâ, i.e. the lower part of the Triassic System composed mainly of marine facies and the upper part of terrestrial strata especially in South China. Although the Global Stratotype Section and Point (GSSP) of the Permian-Triassic boundary is located in South China, the Triassic of China except for some marine Lower-Middle Triassic depositions shows significantly local characteristics and is hardly correlated with the global chronostratigraphic chart. Consequently, the Triassic of China contains not only the international research hotspots but also difficult points in stratigraphic study. This paper aims to present a brief review of the Triassic in China, including chronostratigraphy, biostratigraphy, magnetostratigraphy and chemostratigraphy, and summarize an integrated Triassic stratigraphic framework of China. Accordingly, a stratigraphic correlation is proposed for the lithostratigraphic sequences among the three tectono-paleogeographic stratigraphic regions. The comprehensive study indicates that ammonoids are the classic index fossils in Triassic biostratigraphy but conodonts are more advantageous in the study and definition of the Triassic chronostratigraphic boundaries. China still has the potential to optimize the GSSPs of the Induan-Olenekian boundary and Olenekian-Anisian boundary. The correlation of the Permian-Triassic boundary between marine and terrestrial facies might be achieved with the help of the Permian-Triassic "transitional bed" and its related biotic and environmental events in association with the biostratigraphic study of conchostracan, vertebrate and plant fossils. In addition, the carbon isotopes have been proved to be one of the powerful methods in marine Triassic stratigraphic study, whereas the oxygen and strontium isotopes may be additional important bridges to establish the correlation between the marine and terrestrial strata, but as yet lacking of relevant studies in terrestrial strata. Considering the most stratigraphic intervals of the Triassic and the terrestrial Triassic in China are difficult to be correlated to the global chart, the proposed Chinese (regional) Triassic chronostratigraphic chart of marine and terrestrial stages would be of importance to the study of Chinese Triassic stratigraphy and related aspects, but the stages must be conceptually in line with international standards and studied as soon as possible in order to finalize the definition.
Benjamin A. Black, Ryan R. Neely, Jean-FranÃois Lamarque, Linda T. Elkins-Tanton, Jeffrey T. Kiehl, Christine A. Shields, Michael J. Mills & Charles Bardeen (2018)
Systemic swings in end-Permian climate from Siberian Traps carbon and sulfur outgassing
Nature Geoscience 11: 949â954Â
Siberian Traps flood basalt magmatism coincided with the end-Permian mass extinction approximately 252 million years ago. Proposed links between magmatism and ecological catastrophe include global warming, global cooling, ozone depletion and changes in ocean chemistry. However, the critical combinations of environmental changes responsible for global mass extinction are undetermined. In particular, the combined and competing climate effects of sulfur and carbon outgassing remain to be quantified. Here we present results from global climate model simulations of flood basalt outgassing that account for sulfur chemistry and aerosol microphysics with coupled atmosphere and ocean circulation. We consider the effects of sulfur and carbon in isolation and in tandem. We find that coupling with the ocean strongly influences the climate response to prolonged flood basalt-scale outgassing. We suggest that sulfur and carbon emissions from the Siberian Traps combined to generate systemic swings in temperature, ocean circulation and hydrology within a longer-term trend towards a greenhouse world in the early Triassic.